Aluminum alloy foams, new materials belonging to a special class of porous materials, have been prepared using melt foaming method. Silicon was chosen alloying element due to its low density, high strength, effective casting and reduced shrinkage. Melt foaming method is cost-effective method to fabricate metal foam. Usually, TiH2 is applied to blowing agent, but its cost is high. CaCO3 is one of candidates to substitute TiH2 in the economic view-point. For the comparison of formability, Mg alloy foams were prepared by TiH2 and CaCO3. However, the decomposition temperature of CaCO3 is higher than that of TiH2. This paper will be discussed on the possible usage of CaCO3 in the Al melt.